First of all, that ain't 19 players and the list is a complete joke anyway.
T-Mac, Kidd, Wade, Barkley and Malone ahead of KG?
The only ones in the league history that are clearly ahead of Garnett is the following, in no order;
Jordan
Russell
Chamberlain
Shaq
Bird
Kareem
Magic
Olajuwon
Then you have to rate two guys like Duncan and Kobe ahead of him based on their accolades, although peak Garnett edges Kobe and his and Duncans peaks are a wash basically, although I prefer Garnetts overall impact but it's meh. Erving is kinda iffy, but I wouldn't be surprised if some people ranked him higher.
With that said, Garnett is around ~ 11-12.. possibly 13 at worst all-time although I feel Oscar Robertsons impact is kinda overrated.